In the formation of metal interconnects, for example copper interconnects, depositing a cobalt capping layer between the copper interconnect and the subsequently formed dielectric barrier layer improves the adhesion between the metal and the dielectric and the reliability of the interface between the metal and the dielectric portions. However, the inventors have observed that typical cobalt deposition processes are plasma deposition process utilizing precursors that require a plasma process. The inventors have observed that such a plasma process results in damage to surrounding dielectric materials, for example dielectric materials having a low dielectric constant.
Accordingly, the inventors have developed improved techniques to selectively deposit a cobalt layer on a substrate.